Hi, I'm using the -fsanitize=undefined flag and got a runtime error after a compiler upgrade from 7.2 to 9.3. I was happy at first that the upgraded compiler caught an error that I can fix before it hits me in production. However after some investigation, I cannot figure out what's wrong in the code. That's why I seek help on this mailing list, can someone explain the bug to me? Or is it a bug in the compiler that I should report? The simplified version of the test code on Compiler Explorer: https://godbolt.org/z/7rAxJj It shows that different compiler versions behave differently. There is a comment on line 16 that explicitly defaults the Derived constructor. If you switch the comment with line 17, both compiler verions run fine without producing the runtime error although the defaulted constructor should be exactly the same the user defined one: https://godbolt.org/z/UShm-u Can someone please explain what's wrong? Thanks in advance, Tibor Billes
